This can be proven for any valid argument form using a truth table which shows that there is no situation in which there are all true premises and a false conclusion.
Founded in 1994, IntraLearn Software Corporation (ISC) is a pioneer of creating e-Learning and Knowledge Organization products for corporate enterprises, academic institutions, associations, government agencies and training suppliers.
Ameritech was acquired by SBC Communications in 1999 which subsequently acquired AT&T Corporation in 2006, becoming the present-day AT&T Inc.